I'm a picky investor. I buy only the highest-quality growth stocks I can find.

I look for companies that are rapidly improving their financial statements, boast a strong competitive position, have a huge growth runway ahead of them, and are trading at an attractive valuation.

I believe Novocure (NASDAQ:NVCR) and Semler Scientific (OTC:SMLR) exhibit all of these key attributes in spades. Here's why I just added to my position in both of them last week.

Stacks of bills arranged from shortest to tallest

Image source: Getty Images.

Novocure

Novocure is on a mission to give people with cancer a fighting chance. The company is commercializing a brand-new modality of cancer treatment, called tumor treating fields (TTFields). This technology makes use of artificially generated electric fields to safely and effectively kill off cancerous tumors.

This idea sounded radical when it was first introduced, but Novocure has won over its critics. The company has steadily convinced payers, patients, and providers to give it a try.

Novocure's financial statements have flourished in response to the growing acceptance. Last quarter, Novocure's revenue jumped 39%. The gains allow margins to expand across the board, and the business is starting to produce steady profits.

I think Novocure's future looks exceptionally bright for two reasons.

First, no other company has commercialized a TTFields therapy. That means Novocure literally has this market all to itself.

Second, Novocure is currently in late-stage trials to expand the labeling for TTFields to be used in brain metastases, lung cancer, pancreatic cancer, and ovarian cancer. Winning approval in any of these indications would dramatically expand the company's addressable market.

Despite all of these positives, Novocure's stock is down 35% from its 2019 highs. I gleefully added to my position last week.

Semler Scientific

Millions of Americans have peripheral artery disease (PAD) -- a narrowing of the arteries due to the progressive buildup of fat -- but they don't even know it. That's troubling because people with PAD face a significantly greater chance of suffering a heart attack or stroke.

Semler launched an innovative product, called QuantaFlo, that helps address this problem. QuantaFlo is a clip placed onto a patient's toes and fingers during a routine checkup. In just a few minutes, QuantaFlo produces a report that shows how blood is flowing to each of the extremities. Patients and providers thus get the information they need to take action before a medical emergency arises.

QuantaFlo is gaining rapid popularity, and in turn Semler has been posting mouthwatering financial results. Revenue jumped 39% last quarter, margins expanded, and net income expanded 44%. These numbers are even more impressive considering the company generates less than $10 million in quarterly revenue.

What excites me most about Semler is that its growth runway looks huge. There are more than 300,000 physicians in the U.S. alone who could test their patients regularly with QuantaFlo, but only a small minority of them currently do. Profits are poised to continue growing at a fast clip as the company convinces more physicians to get on board.

Even though Semler already produces profits and boasts huge potential, its stock isn't crazy expensive. Shares currently trade hands for around 24 times next year's earnings estimates.

In my opinion, that's too good a deal to pass up.